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<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>Susan G. Buto</dc:contributor>
  <dc:contributor>David W. Smith</dc:contributor>
  <dc:contributor>Nora C. Nelson</dc:contributor>
  <dc:creator>Michael T. Moreo</dc:creator>
  <dc:date>2020</dc:date>
  <dc:description>&lt;p&gt;This report documents methodology and results of a study that estimated groundwater discharge by evapotranspiration (&lt;i&gt;GWET&lt;/i&gt;) from phreatophytic vegetation in two desert riparian areas with ephemeral spring discharge in Clark County, southern Nevada. The phreatophytes consisted primarily of western honey mesquite [&lt;i&gt;Prosopis glandulosa&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/i&gt;&lt;span&gt;var.&amp;nbsp;&lt;/span&gt;&lt;i&gt;torreyana&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/i&gt;&lt;span&gt;(L.D. Benson) M.C. Johnst.&lt;/span&gt;] at Stump Spring and mixed shrubs at Hiko Springs. An eddy-covariance station and precipitation gage were established to concurrently measure actual evapotranspiration (AET) and precipitation. Site-scale &lt;i&gt;GWET&lt;/i&gt; rates—computed by subtracting measured precipitation from AET—were 239 ±45 millimeters per year (mm/yr) based on measurements over one growing season at Stump Spring and 109 ±27 mm/yr averaged over two growing seasons at Hiko Springs.&lt;/p&gt;&lt;p&gt;The volume of &lt;i&gt;GWET&lt;/i&gt; for each groundwater discharge area (GDA) was estimated by developing relations between site-scale computed &lt;i&gt;GWET&lt;/i&gt; rates and phreatophytic vegetation represented by a Normalized Difference Vegetation Index (NDVI). A GDA was delineated for the natural drainage in each area by mapping the extent of phreatophytes using high-resolution imagery. A second GDA was delineated at Stump Spring by mapping the extent of phreatophytes in the Area of Critical Environmental Concern (ACEC). Site-scale &lt;i&gt;GWET&lt;/i&gt; rates were scaled up by applying the site-based &lt;i&gt;GWET&lt;/i&gt; -NDVI relations to NDVI distributions in each GDA. The areas of phreatophytic vegetation within each GDA, area-weighted mean &lt;i&gt;GWET&lt;/i&gt; rates, and &lt;i&gt;GWET&lt;/i&gt; volumes were as follows: (1) Stump Spring—59 hectares (ha), 126 mm/yr, 7.4 ± 1.4 ×104 cubic meters per year (m&lt;sup&gt;3&lt;/sup&gt;/yr) (60 ± 11 acre-feet/yr); Stump Spring ACEC—49 ha, 98 mm/yr, 4.9 ± 0.9 × 104 m&lt;sup&gt;3&lt;/sup&gt;/yr (39 ± 7 acre-feet/yr); and (2) Hiko Springs—7.2 ha, 112 mm/yr, 0.8 ±0.2 × 104 m&lt;sup&gt;3&lt;/sup&gt;/yr (6.6 ±1.6 acre-feet/yr). The &lt;i&gt;GWET&lt;/i&gt; rate computed at Stump Spring compared favorably with published &lt;i&gt;GWET&lt;/i&gt; rates for mesquite.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.3133/sir20205075</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>U.S. Geological Survey</dc:publisher>
  <dc:title>Estimates of groundwater discharge by evapotranspiration, Stump Spring and Hiko Springs, Clark County, southern Nevada, 2016–18</dc:title>
  <dc:type>reports</dc:type>
</oai_dc:dc>